Vibratory core for concrete pipe making machine

ABSTRACT

A novel vibrating core apparatus for use with a concrete pipe making machine. The novel apparatus includes a core, vertically movable into and out of a pipe form, a series of vibrators attached along the interior side wall of the core, an upwardly movable system operative by fluid pressure for raising and lowering the core, and an interlocking connection between a standard packerhead, which distributes cementitious material about the interior of the pipe form, and the upper portion of the core. The packerhead is designed to rotate while forming the pipe; the core does not rotate and the connecting means between the two is easily attached and disengaged from the packerhead.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of Ser. No. 638,010, filed May 12, 1967now abandoned.

BACKGROUND OF THE INVENTION

The invention relates generally to the formation of concrete pipe, andparticularly presents a solution to the problem of residual straincreated by the troweling of zero slump concrete with rotary motion. Inthe usual pipe forming apparatus, the outer form of the pipe isstationary. Thus, rotary motion by the packerhead imparts a stress tothe concrete mix, such stress being particularly disturbing in the eventthe concrete pipe is supplied with reinforcing wire. It has been foundthat such wire may be strained beyond its yield point causing permanentbending as well as deflection of the wire, making the completed pipeproduct unsatisfactory. Furthermore, because of the difference inmodulus of elasticity between steel and concrete relieving suchundesirably induced stress after the pipe is formed causes unnecessaryvoids to be formed in the concrete pipe. Obviously, such voids reducethe strength of cured pipe and allow leakage in the pipe through thevoids.

In the case of non-reinforced pipe residual stress movement of theconcrete causes cracks to form in the pipe thereby reducing strength ofthe pipe and permitting leaks. As a result of these encounteredproblems, many purchasers of concrete pipe refuse to accept pipe formedby a rotating packerhead or roller-head method.

The prior art is not entirely devoid of vibrating cores used in themanufacture of concrete pipe. For example, the U.S. Pat. to E. Robbins,No. 1,504,834, illustrates a core for a pipe form inserted into andwithdrawn from the form therebeneath by means of controlled fluidpressure. U.S. Pat. No. 1,961,981 to Pechstadt also discloses a movablecore for a pipe form, and a tamper for compacting the cementitiousmaterial. A further improvement to the basic concept of these twopatents is disclosed by U.S. Pat. No. 2,544,453 to Gaudin whichillustrates a vertically movable vibrating core insertable into andwithdrawable from a pipe form.

However, none of these patents nor any material presently available inthe art of forming concrete pipes discloses a solution to the residualstress problem discussed above which is encountered in the currentpractice of the manufacture of pipe which employs the use of avertically disposed form and a packerhead which moves slowly along theaxis of the form while rotating and while concrete is poured in to formthe pipe.

The instant invention overcomes the disadvantages of the prior art bypermitting the formation of concrete pipe by the rotating packerheadmethod without inducing residual stress either in the concrete or in thereinforcing wire, if used. By employing a vibrating core together with arotating packerhead as the concrete pipe is formed, residual stressesare avoided due to vibratory motion being imparted to the concrete andreinforcing wire during the pipe forming operation. Of furthersignificance is the fact that the vibrating core of this invention maybe used on concrete pipe formed by a variety of other methods such as byspinning, vibration, or tamping, before the pipe is cured so as torelieve all residual stress, fill voids, compact and densify theconcrete and induce a more intimate bond between reinforcing wire andthe concrete mix prior to curing of the pipe. Finally, desirably largeraggregate may be used in the concrete mix for concrete pipes resultingin a decrease in absorption of the pipe wall because vibration by thecore will cause thorough mixing of the concrete as well as a bettercoating of sand and aggregate particles with cement.

SUMMARY

The object of the invention is to provide a concrete pipe makingapparatus which completely negates residual strain caused by thestandard pipe forming apparatus by employing a vertically movableinternal vibrating core to the pipe as it is formed. In the primaryembodiment, the vibrating core is adapted for use with a rotatingpackerhead as the concrete pipe is formed. Hydraulically actuatedinterengaging means is provided between the packerhead and the vibratingcore which permits rotation to be imparted to the packerhead whileallowing the vibrating core to remain axially stationary. Primary liftmeans is provided for the packerhead and core; fluid pressure actuatedmeans is provided beneath the vibrating core to move the same downwardlyafter the pipe forming operation. The interengaging means ishydraulically disengaged at the completion of the pipe forming operationto allow removal of the packerhead and withdrawal of the vibrating corefrom the completed, uncured pipe so that the uncured pipe together withthe outer form thereof may be removed from the pipe making machine sothat a new outer form may be set into place for formation of anotherpipe.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of construction and operation according to the preferredembodiments of the invention will become readily apparent by referenceto the following drawings wherein:

FIGS. 1 through 5 are front elevational views showing the invention asapplied to a concrete pipe making machine of the type commonly used inthe industry; these figures show the sequence of operations in formingconcrete pipe;

FIGS. 6 through 9 are similar to FIGS. 1 through 5 and show the sequenceof operations in forming a concrete pipe according to this invention inanother embodiment; and

FIG. 10 is a sectional view of the means interengaging the vibratingcore and the rotating packerhead and applies to both embodiments of theinvention as shown by FIGS. 1 through 5 and by FIGS. 6 through 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings by reference character and in particularto FIGS. 1 through 5 thereof, the invention is shown in combination witha modified pipe making machine of the type commonly used in the industrytoday. The pipe making machine comprises a pipe form 10 of generallycylindrical configuration, which may have circular corrugations therein.Form 10 includes an upper, spigot end 12 and a lower, divergingfrusto-conical skirt forming a bell end 14. A platform 16 is providedfor form 10, and includes a circular opening 18 centrally locatedbeneath bell end 14. Platform 16 may be a turntable for indexing ofwork.

Interiorally of bell end 14 is a pallet 20 having a circular opening 22therein, generally concentrically spotted with respect to opening 18 inplatform 16. Pallet 20 is slightly movable vertically within bell end 14for initial formation of the bell end of the pipe.

A frame superstructure generally indicated by 24 is located aboveplatform 16 and includes a cementitious material boot or hopper 26 and aconveyor 28 for filling form 10. Numeral 30 indicates a packerhead,rollerhead, or circular, powered trowel, each of which is known in theart, which distributes and compacts material against the form from bellend 14 upwardly to form the pipe, travelling through mix provided fromboot 26 and conveyor 28. Frame 24 supports a vertically movablecrosshead (not shown) which drives shaft 34 and distributor 30.

A pit designated at 36 contains the major portion of the instantinvention. For ease of explanation, parts will be described from thebase of pit 36, upwardly to turntable or platform 16. Mounted in thebase of pit 36 is a caisson or hydraulic cylinder 38 having an internalvertically travelling piston (not shown) operatively connected to apiston rod 40 (FIG. 2). A frame assembly comprising a plurality ofradially spaced vertical standards 42, 42 is arranged concentricallyabout cylinder 38 and beneath opening 18 in platform 16. A circular baseblock plate 44 is secured about cylinder 38 at the floor of pit 36 tostandards 42, 42. A similar upper block plate 46 is mounted near theupper ends of standards 42, 42. Between plates 44 and 46 are located aseries of radially spaced guide rods 48, 48. Plates 44 and 46 serveadditionally as the lower and upper limits respectively of the travel ofa bearing block assembly 50, having bearing sleeves formed therein (notshown) about guide rods 48, 48, for free movement therealong. Blockassembly 50 cooperating with guides 48, 48 also serves to prevent axialrotation of the vibrating core 60 of the invention.

A cylindrical support casing 52 is mounted on top of block assembly 50and is affixed to the free end of piston rod 40. A circular opening 54is provided in the lower face of casing 52 to entry of cylinder 38 whenthe invention is in a static, initial stage as shown in FIG. 1. A thrustrod 56 is fixed to piston rod 40 through the upper portion of casing 52having core platform support 58 mounted thereon. Thus axial stabilityand limitation of travel of core 60 are imparted substantially beneaththe lower terminal end of core 60 so that complete insertion into form10 is allowed, without interfering with the other operating parts of theapparatus, as shown in FIG. 4. Vibrating core 60 is mounted directly onplatform 58 being provided with a series of internally spaced vibrators62 (FIG. 3).

Immediately beneath platform 16 is a pallet lift assembly 64 (FIG. 2)for forming the bell end of the pipe in the initial stage of operation.Such an assembly is described in detail in U.S. Pat. No. 3,083,433 to M.Tiller. For purposes of the instant invention, assembly 64 (FIG. 2)includes a vibrating plate 66 having legs 68 thereon for contacting,lifting and vibrating pallet 20. A drive plate 70 is secured to andimmediately beneath vibrating plate 66, plates 66 and 70 being rotatablymounted in frame 42. A motor with suitable gearing drives plate 70 torotate pallet 20 during the bell forming stage of the pipe makingoperation. Assembly 64 is raised and lowered by suitable lift means (notshown) and is limited in travel by a pair of limit stops 72, 74.

A second embodiment of the invention is shown in FIGS. 6 through 9wherein the pipe is formed without aid of pallet lift assembly 64. As inthe embodiment illustrated in FIGS. 1 through 5, the pipe making machineincludes a bell-down form 10, super-structure 24, packerhead 30 withdrive shaft 34, a material hopper 26 and platform or turntable 16. Inpit 36 is a caisson or hydraulic cylinder 38 having a piston rod 40actuated by fluid pressure. Core platform 58 is mounted directly onpiston rod 40 (FIG. 8). Controlled movement for platform 58 is providedby a plurality of radially spaced rods 76, 76 mounted directly in thefloor of pit 36 and secured at their upper ends to frame portions 78beneath platform 16. Vibrators 80, 80 are attached to bell end 14 ofform 10 to compact material in the bell of the pipe, formed betweenpallet 20 and form 10. Finally, rollers 82, 82 are mounted beneathplatform 16 to frame 78 to guide core 60 into and out of form 10.

FIG. 10 illustrates the specific connection between rotating packerhead30 and non-rotating core 60. Packerhead 30 includes an internal rotatingdrive shaft 84 which is threaded at its terminal end 86 to receive abearing and pilot stud housing 88. Non-rotating support shaft 90 ismounted internally of rotating housing 88 by means of a twin series ofinclined roller thrust bearings 92, 92 which are adapted to receive bothaxial and radial stress on the order of 20,000 pounds and 10,000 poundsrespectively. A pilot stud 94 is formed on the lower end of supportshaft 90 and is tapered at its thrust end so as to guide itself intolock housing 96 of non-rotating core 60 without aid of external guidemeans. Pilot stud 94 is formed with a lock recess 98 which cooperateswith radially spaced locking studs 100, each actuated by hydraulicpressure through lines 102 against piston 104. Studs 100 and recess 98are formed with cambered abutting faces so that upon relief of pressurein lines 102, pilot stud 94 will separate from core lock housing 96 byaxial movement above, forcing lock studs 100 into their receivingchambers 106.

The operation of the two embodiments of the invention are similar. Inthe embodiment shown in FIGS. 1 through 5, the invention is depictedfirst, in FIG. 1, in a static position prior to the pipe makingoperation. In this position, platform or turntable 16 may be moved (nowshown) to place form 10 into position, centrally beneath packerhead 30and above core 60.

The pipe forming operation begins by the lowering of packerhead 30together with housing 88 and pilot stud 94 into form 10 and the raisingof core 60 by fluid pressure in cylinder 38. Hydraulic pressure isintroduced through lines 102 to force studs 100 into recess 98 so thatrotating packerhead or rollerhead 30 and core 60 are firmly engaged. Mixis then poured into form 10 from conveyor 28, and pallet lift assembly64 is raised to the position shown in FIG. 2. The bell end of the pipeis then formed in the manner disclosed in U.S. Pat. No. 3,083,433, asdiscussed above, by rotating and vibrating the pallet assembly 64.Rotation of packerhead 30 is initiated, in a direction opposite therotation of pallet 20.

When the bell end portion of the pipe has been completed, assembly 64 islowered to the static position shown in FIG. 3. Packerhead 30 is thenraised through the mix, together with core 60 which is forced upwardlyby fluid pressure in cylinder 38 acting through piston rod 40, thrustrod 56, and core platform 58. As each vibrator 62 passes bell-end 14 ofform 10, it is activated by a trip switch or other suitable energizingmeans (not shown) to vibrate that portion of the core. When packerhead30 has reached the top or spigot end 12 of form 10, rotation ceases,fluid pressure in line 102 is relieved, and packerhead 30 is lifted fromcore 60, as illustrated in FIG. 4. Vibration of core 60 by vibrators 62is continued for a short time to complete compaction of mix,particularly around spigot end 12 of form 10, and to assure the completeelimination of any residual stress in the completed pipe which may havebeen caused by the rotation of packerhead 30.

Once vibration is satisfactorily completed core 60 is withdrawn from thefinished pipe by cylinder 38, turntable 16 is moved to place a new form10 into position and to remove the newly completed green pipe.

.[.Of course, vibrators 62 might be replaced by, or supplemented withvibrators located externally of the invention, as on form 10 (notshown). The important point is that vibratory motion be imparted to themix as the pipe is being formed to assure complete compaction of themix..].

The operation of the second embodiment of the invention shown in FIGS. 6through 9 is similar, except that bell end 14 of the pipe is formed byvibration induced by vibrators 80 located therearound. Once the bell endis formed, vibrators 80 are turned off, and the remainder of theoperation discussed above is completed.

Green pipe formed from cementitious material by a rotary trowel methodor other methods common in the art may be transferred to the inventionwhile still in its mold to be vibrated by insertion of core 60thereinto. This operation will remove residual stress in the green pipeand give the cured pipe the structural integrity assured by use of thepresent invention during the initial forming stage of the pipe.

Three-edge bearing tests were made on concrete pipe formed by theinvention and results were compared with results obtained from testingpipe manufactured without the aid of the instant invention. Five testspecimens were manufactured having only 74 percent of the steelreinforcement used in our specimens manufactured by the older process.These tests were conducted to specifications for three-edge bearingtests contained in "TENTATIVE SPECIFICATIONS FOR REINFORCED CONCRETECULVERT, STORM DRAIN AND SEWER PIPE" (C 76-63T), published by theAmerican Society for Testing and Materials in 1963. The values listed inthe D-load columns below are test loads expressed in pounds per linearfoot per foot of pipe diameter. The four specimens manufactured by theolder process were made according to the ASTM requirements for Class IVreinforced concrete pipe. The test results of the pipe manufacturedaccording to the invention were as follows:

                    D-load      D-load                                            Made   Tested   0.01" crack Ultimate  Vibrated                                ______________________________________                                        x      x+2 days 2200 lbs.   3380 lb.  5 min.                                  x      x+3 days 2024 lbs.   3705 lb.  5 min.                                  x      x+3 days 2102 lbs.   3477 lb.  5 min.                                  x      x+3 days 2124 lbs.   3306 lb.  4 min.                                  x      x+3 days 1893 lbs.   3293 lb.  2 min.                                  ______________________________________                                    

Each pipe was 8 feet long, 2 feet in diameter and had a wall thicknessof 3 inches, and was given 10 hours of moist curing.

The four specimens manufactured in the manner known in the art yieldedthe following test results:

                         D-load      D-load                                       Made     Tested      0.01" crack Ultimate                                     ______________________________________                                        x        x+50 days  2400 lb.     3280 lb.                                     x        x+20 days  2020 lb.     3100 lb.                                     x        x+10 days  1970 lb.     3320 lb.                                     x        x+25 days  2100 lb.     3470 lb.                                     ______________________________________                                    

These latter specimens compare precisely in size to the former, savethat these four specimens contained a significantly greater amount ofreinforcing steel, and were aged for a considerably longer period oftime. Yet the pipes formed according to the present invention performedas well as those made in a usual manner.

We claim:.]. .Iadd. What I claim and desire to secure by Reissue LettersPatent is: .Iaddend.
 1. In a concrete pipe forming apparatus adapted forforming pipe from zero-slump concrete including a pipe form, a platformfor supporting said pipe form, a rotating packerhead materialdistributor comprising a rollerhead for forming the pipe, and a poweredmain lift mechanism for raising said rollerhead as the pipe is formed,the improvement comprising:a. a non-rotating core; b. means forvibrating material forming the pipe as the pipe is formed; c. meansinterengaging said core with said rollerhead; and d. an upwardly movableguide system for said core.[...]..Iadd., said means for vibratingmaterial forming the pipe as the pipe is formed comprising meansattached to the core for vibrating the core. .Iaddend. .[.2. Theapparatus of claim 1 wherein said means for vibrating material formingthe pipe as the pipe is formed comprise means attached to the core forvibrating the core..].
 3. The apparatus of claim .[.2.]. .Iadd.1.Iaddend.wherein said means attached to the core for vibrating the coreinclude a plurality of vibrators, spaced vertically along the interiorwall thereof, each of said vibrators being selectively actuable.
 4. Theapparatus of claim 3 wherein the means for selectively actuating thevibrators comprise means for energizing each of said vibrators as saideach vibrator passes beneath the lower terminal edge of said pipe formas said core enters the pipe form.
 5. The apparatus of claim 1 whereinsaid upwardly movable guide system for said vibratory core comprises:a.a fluid pressure cylinder, located concentrically beneath said core; b.a piston in said cylinder; c. a piston rod on said piston; d. a supportplatform for said core operatively mounted on said piston rod; e.vertical guide rods radially spaced about said piston rod and extendingupwardly toward said platform; and f. means connecting said guide rodsand core platform whereby rotational movement of said core is prevented.6. The apparatus of claim 5 wherein said means connecting said guiderods and core platform comprise:a. a cylinder easing support, dependingfrom said core platform, about said piston rod and fluid cylinder; andb. a bearing block assembly, depending from said casing and itnerengagedfor sliding movement with said guide rods, whereby lateral and axialstability is imparted to said core substantially beneath the thrust endof said piston rod.
 7. The apparatus of claim 6 wherein said guide rodsare further provided with upper and lower stops defining the verticallimits of movement of said bearing block assembly.
 8. The device ofclaim 1 wherein said means interengaging said distributor and said corecomprise:a rotatable housing, firmly secured to and depending from saiddistributor, axially thereof; b. a non-rotating support shaft, dependingaxially from said rotatable housing; c. bearing means interconnectingsaid support shaft and housing allowing free rotation of said housingaround said support shaft; d. a lock housing mounted on the upper freeend of said core; and e. disconnectable securing means acting betweensaid lock housing and said support shaft.
 9. The interengaging means ofclaim 8 wherein said bearing means comprise a plurality of inclinedbearings adapted to receive thrust and radial loading.
 10. Theinterengaging means of claim 8 wherein said disconnectable securingmeans comprise:a. a male pilot stud on said support shaft; b. a femalelock sleeve in said lock housing; c. means defining a recesscircumferentially about said pilot stud; and d. a plurality of fluidpressure actuable lock studs in said sleeve adapted to enter saidrecess.
 11. The disconnectable securing means of claim 10 wherein saidlock studs and said core are formed with inclined mating faces wherebyupon relief of fluid pressure on said lock studs and axial separation ofsaid core and distributor, said lock studs are withdrawn into said lockhousing thereby permitting axial separation of said core from saiddistributor.
 12. The invention as recited in claim 1 wherein the pipeform contains a reinforcing wire structure for the pipe.
 13. In aconcrete pipe forming apparatus adapted for forming pipe from zero-slumpconcrete including a pipe form, a platform for supporting said pipeform, a rotating packerhead material distributor comprising a rotatingtrowel for forming the pipe, and a powered main lift mechanism forraising said rotating trowel as the pipe is formed, the improvementcomprising:a. a non-rotating core; b. means for vibrating materialforming the pipe as the pipe is formed; c. means interengaging said corewith said rotating trowel; and d. an upwardly movable guide system forsaid core.[...]..Iadd., said means for vibrating material forming thepipe as the pipe is formed comprising means attached to the core forvibrating the core. .Iaddend. .[.14. The apparatus of claim 13 whereinsaid means for vibrating material forming the pipe as the pipe is formedcomprise means attached to the core for vibrating the core..].
 15. Theapparaus of claim .[.14.]. .Iadd.13 .Iaddend.wherein said means attachedto the core for vibrating the core include a plurality of vibrators,spaced vertically along the interior wall thereof, each of saidvibrators being selectively actuable.
 16. The apparatus of claim 15wherein the means for selectively actuating the vibrators comprise meansfor energizing each of said vibrators as said each vibrator passesbeneath the lower terminal edge of said pipe from as said core entersthe pipe form.
 17. The apparatus of claim 13 wherein said upwardlymovable guide system for said vibratory core comprises:a. a fluidpressure cylinder, located concentrically beneath said core; b. a pistonin said cylinder; c. a piston rod on said piston; d. a support platformfor said core operatively mounted on said piston rod; e. vertical guiderods radially spaced about said piston rod and extending upwardly towardsaid platform; and f. means connecting said guide rods and core platformwhereby rotational movement of said core is prevented.
 18. The apparatusof claim 17 wherein said means connecting said guide rods and coreplatform comprise:a. a cylindrical casing support, depending from saidcore platform, about said piston rod and fluid cylinder; and b. abearing block assembly, depending from said casing and interengaged forsliding movement with said guide rods, whereby lateral and axialstability is imparted to said core substantially beneath the thrust endof said piston rod.
 19. The apparatus of claim 18 wherein said guiderods are further provided with upper and lower stops defining thevertical limits of movement of said bearing block assembly.
 20. Thedevice of claim 13 wherein said means interengaging said distributor andsaid core comprise:a. a rotatable housing, firmly secured to anddepending from said distributor, axially thereof; b. a non-rotatingsupport shaft, depending axially from said rotatable housing; c. bearingmeans interconnecting said support shaft and housing allowing freerotation of said housing around said support shaft; d. a lock housingmounted on the upper free end of said core; and e. disconnectablesecuring means acting between said lock housing and said support shaft.21. The interengaging means of claim 20 wherein said bearing meanscomprise a plurality of inclined bearings adapted to receive thrust andradial loading.
 22. The interengaging means of claim 20 wherein saiddisconnectable securing means comprise:a. a male pilot stud on saidsupport shaft; b. a female lock sleeve in said lock housing; c. meansdefining a recess circumferentially about said pilot stud; and d. aplurality of fluid pressure actuable lock studs in said sleeve adaptedto enter said recess.
 23. The disconnectable securing means of claim 22wherein said lock studs and said core are formed with inclined matingfaces whereby upon relief of fluid pressure on said lock studs and axialseparation of said core and distributor, said lock studs are withdrawninto said lock housing thereby permitting axial separation of said corefrom said distributor.
 24. The invention as recited in claim 13 whereinthe pipe form contains a reinforcing wire structure for the pipe.